Whats the total amperage available for the 12V rail(s)? That will tell you if you can. My guess would be no. Perhap brand new, but I doubt a 4year old 400W PSU will handle the load well. They just weren't designed to output that much 12V power that far back.

Your PSU is old enough(5 years) and just 400W, i think now is the time to upgrade with the new one... U don't want the possibility your PSU will fry everything inside the case, right?just spend another $50-$70 for a great brand new PSU...

The P55-GD45 has a 4pin connector for CPU and 24pin for motherboard. All available on this Fortron PSU. The only thing is that I have to use two molex-connectors to power the graphic card and only two remain other remain to power 5 SATA hard drives, and 120mm fans. There's one SATA connector directly connected to the PSU for powering the SATA DVDRW...

I'll probably have a go with the OCZ Z-Series 650W or the OCZ ModXStream Pro 500W. Depends on availabilty at the local store, since I need this PC up and running today.

For your config, Corsair VX550W, Antec TP-550 is enough. 650W is overkill. If you are planning to go in for an SLI/CF config in the future then only get a PSU of more than 650W.I would recommend the Corsair, coz its one of the best brands and availability should be good.

Why all this power supply nonsense.I have the same 5 year old power supply running an X2@2.4 2gig ram ,4650 on a Nforce 4 motherboard. It has Active pfc. If power supply dies it only takes out the power supply. It is also adjustable. With variable pots inside to adjust output voltage.

When new it would put out arround 475 watt. Fortron always under rated their power supplys.

Why all this power supply nonsense.I have the same 5 year old power supply running an X2@2.4 2gig ram ,4650 on a Nforce 4 motherboard. It has Active pfc. If power supply dies it only takes out the power supply. It is also adjustable. With variable pots inside to adjust output voltage.

When new it would put out arround 475 watt. Fortron always under rated their power supplys.

yeah, u just running a 4650 on that computer, no objection that the PSU is still running...many people had experience that if the PSu dying or die it will take the other components as well.